If you are going to dig in and do something with a database handle directly, the recommended way is:

use Data::Dumper;
$schema->storage->dbh_do( sub {
    my ( $storage, $dbh ) = @_;
    print Dumper $dbh->selectall_arrayref(
        'select enum_range(typename);',
        { slice => {} }
    );
} );
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The dbh_do method (documented in DBIx::Class::Storage::DBI) gives you the benefit of things like automatic reconnection to the database if your connection has timed out or the server has been restarted.

Also, db_Main is from Class::DBI, not DBIx::Class, although there is a CDBICompat component that will make the latter work mostly like the former (though in the long run you will be better off by just learning the DBIx::Class way, rather than using CDBICompat).